Modern automobiles have on-board computers facilitating vehicle operation and enabling various safety features. Active safety and driver assistance (ASDA) applications require an accurate awareness of vehicle position with respect to a road and other vehicles. Exemplary ASDA applications include navigation applications, lane-keeping and lane centering applications, autonomous driving, and collision-avoidance applications.
For some advanced ASDA operations, accurately positioning the vehicle within a particular lane of a road (lane-level accuracy), not just on-the-road resolution, is needed. Such operations include accurately determining (i) that another vehicle is in the host vehicle path and a separation distance to the other vehicle is decreasing rapidly, (ii) whether the host vehicle is deviating from an intended lateral position (e.g., lane center), and (iii) whether the host vehicle or a nearby vehicle is straying from its present lane, and so possibly changing lanes. Lane-level accuracy generally equates to positioning accuracy within about one meter.
To date, to achieve vehicle positioning of the desired accuracy, correction from a source external to the vehicle has been required. For example, assistance has been provided to the standard global positioning system (GPS) in relative-positioning or differential GPS (DGPS), wide area augmentation system (WAAS) GPS, and combinations of the two.
A primary drawback of such systems is that they inherently rely on the infrastructure additional to the basic GPS. This dependence renders the vehicle less autonomous, and use of the external infrastructure sometimes comes at an added financial cost and/or additional processing cost in terms of time and use of computing resources.
On-board systems have also been used in vehicle positioning. Exemplary systems are inertial-movement units and systems using wheel sensors. These systems, though, cannot be heavily relied upon alone as they inherently accumulate error rather rapidly over time and must themselves be supplemented with accurate positioning updates from the external systems.